Specification ASTM A 217 Gr. C5 provides a nominal 5 percent chromium casting steel widely utilized in the industry for casting relatively large parts such as pump casings. One of the major shortcomings of this material is the fact that it requires preheat to prevent cracking when performing operations such as cutting off of gates and risers and welding.
In U.S. Pat. No. 4,045,256, issued Aug. 30, 1977, an improved 5 percent chromium alloy was disclosed which eliminated the cracking problem during cutting of gates, etc., and welding without preheat. Although the new alloy exhibited comparable impact properties to ASTM A 217 Gr. C5, some applications such as given in ASTM A 352 require better low temperature impact properties.
It is the object, therefore, of this invention to teach a modified nominal 5 percent chromium casting alloy having mechanical properties essentially equal to or superior to that of ASTM A 217 Gr. C5 including impact properties and does not require preheat for performing operations such as mentioned above.
It is further the object of this invention to provide a casting alloy that is less costly and troublesome to produce through the final stages of production flow through the foundry and machine shop.
Generally, the object of this invention is to teach a nominal 5 percent chromium casting alloy which is similar to ASTM A 217 Gr. C5 in chemistry, but has a lower carbon content, nickel additions, and a unique heat treatment for this type of alloy to achieve superior working properties, equal or superior tensile properties and superior impact properties.
Specifically, the object of this invention is to teach a nominal 5 percent chromium casting alloy similar to ASTM A 217 Gr. C5 but having a maximum carbon content of approximately 0.06 percent and nickel additions of nominally 3.0 percent, and which is manufactured with a unique heat treatment to provide superior impact properties.
Specifically, the object of this invention is to teach a 5 percent chromium casting alloy having a maximum carbon content of 0.04 percent, nickel additions of nominally 3 percent, maximum silicon content of 0.75 percent, and maximum aluminum content of 0.12 percent, and which is manufactured with an unique heat treatment to provide superior impact properties which can replace some of the alloys given in ASTM A 352; for example, LCA, LCB, LCC, LC1, and LC2.